We apply different voltages to two materials and record the current in order to determine the resistance. The two materials are a resistor and a light bulb. My problem has occured when graphing though.

I know that the relationship for an ohmic material is linear, therefore it's simply (1/R). This would be true for the resistor. The lightbulb however is a nonohmic material, therefore it's not a linear relationship.

The way my graph looks is not the same as in the book though. The book shows a graph which looks like an exponential function (x^2), approaches a verticle asymptote. My graph for the lightbulb though looks opposite (looks more like a sqrt function) and approaches a horizontal asymptote. When looking online I saw a V versus I graph for a filament and it looked the same as mine.

My question is, why is this? Why do I have a different graph than what the book shows for a nonohmic material, but I see other "filament" graphs look the same as mine.

Thanks.